EENY467

Boisduval Scale, Diaspis boisduvalii Signoret (Insecta: Hemiptera: Diaspididae)1

Adriana Espinosa, Heidi Bowman, Amanda Hodges, and Greg Hodges2

1. This document is EENY467, one of a series of the Department of Entomology and Nematology, UF/IFAS Extension. Original publication date November 2009. Revised June 2010 and September 2016. Visit the EDIS website at http://edis.ifas.ufl.edu. This document is also available on the Featured Creatures website at http://entnemdept.ifas.ufl.edu/creatures/.

2. Adriana Espinosa, former Extension assistant; Heidi Bowman, graduate student; Amanda Hodges, SPDN assistant director in entomology and training/education; UF/IFAS Extension; and Greg Hodges, Florida Department of Agriculture & Consumer Services, Division of Plant Industry; UF/IFAS Extension, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.

IntroductionThe boisduval scale, Diaspis boisduvalii Signoret, is an economically important pest of orchids and was reported as the most important insect pest of orchids in Florida (Dekle 1965). Miller and Davidson (2005) list boisduval scale as one of the 43 most serious worldwide armored scale pests.

DistributionThe boisduval scale occurs throughout the tropics and as a greenhouse pest in more temperate climates (Dekle 1965, Miller and Davidson 2005).

DescriptionFemales are white to light yellow, approximately 0.05–0.09 inches (1.2–2.25 mm) in diameter, circular or oval in shape, and covered with a centrally located, white-transparent, flat circular or oval shed skin. When the scale cover is removed, a single, horn-like projection on either side of the body, near the head and thorax may be visible (Dekle 1965, Howard et al. 2001, Miller and Davidson 2005).

Males are oval to elongate in shape, with a white cover and marginal shed skin. Males measure approximately 0.04 inches (1mm) in length.

Life CycleEach adult female may produce up to 200 eggs and live as long as seven months. Eggs hatch within five to seven days and become crawlers. Egg color depends upon maturity, and ranges from clear to yellow, and finally orange. The development from egg to the adult stage averages 33 days for males and 50 days for females (Miller and Davidson 2005).

Figure 1. Adult female boisduval scales, Diaspis boisduvalii Signoret, on banana fruit.Credits: Lyle J. Buss, UF/IFAS

2Boisduval Scale, Diaspis boisduvalii Signoret (Insecta: Hemiptera: Diaspididae)

Figure 3. Adult female boisduval scales, Diaspis boisduvalii Signoret, with exuviae present. A centrally-located circle shape is part of the exuviae.Credits: UF/IFAS

Figure 4. Yellow colored body of the adult female boisduval scale, Diaspis boisduvalii Signoret. The oval-shaped cover has been removed.Credits: Avas Hamon, Florida Department of Agriculture and Consumer Services, Division of Plant Industry

Figure 5. Cluster of male boisduval scales, Diaspis boisduvalii Signoret, on Cattleya leaf. Notice the fluffy or cottony appearance.Credits: Heidi M. Bowman, UF/IFAS

Figure 2. Close up view of adult female boisduval scale, Diaspis boisduvalii Signoret, on banana fruit.Credits: Lyle, J. Buss, UF/IFAS

Figure 6. Male, female, and crawler life stages of boisduval scale, Diaspis boisduvalii Signoret, on Cattleya leaf.Credits: Heidi M. Bowman, UF/IFAS

3Boisduval Scale, Diaspis boisduvalii Signoret (Insecta: Hemiptera: Diaspididae)

HostsThis species has been recorded on over 15 families and 65 genera of plants in Florida alone, but is most commonly found on orchids and palms.

Within the palm hosts (family Arecaceae) the following genera are susceptible (Howard et al. 2001, Miller and Davidson 2005):

• Acoelorraphe• Acrocomia• Archontophoenix• Areca• Bactris• Butia—pindo palm• Caryota—fishtail palms• Chamaedorea• Chamaerops—European fan palm or Mediterranean fan

palm• Cocos—coconut palm• Corypha—gebang palm, buri palm or tailpot palm• Dictyosperma• Dypsis• Elaeis—oil palms• Euterpe• Howea• Hyophorbe• Latania—latan palm• Livistona• Nannorrhops—mazari palm• Phoenix• Ptychosperma• Rhapidophyllum—needle palm• Raphis• Roystonea—royal palms• Sabal—palmetto or fan palms• Syagrus• Thrinax• Trachycarpus—fan palms• Washingtonia

Recorded orchid hosts (Orchidaceae) include the following genera:

• Acineta• Angraecum• Anguloa• Bletia• Brassavola• Brassia• Brassocattleya

• Broughtonia• Bulbophyllum• Cattleya• Caularthron• Coelogyne• Cycnoches• Cymbidium• Dendrobium• Encyclia• Epidendum• Laelia• Maxillaria• Miltonia• Neofinetia• Odontoglossum• Oncidium• Ornithidium• Peristeria• Pleurothallis• Renanthera• Rhynchostylis• Schomburgkia• Sophronitis• Stanhopea• Trichopilia• Vanda• Xylobium

Other recorded host plant families include:

• Agavaceae• Amaryllidaceae—Agave sp.• Anacardiaceae—Mangifera indica, mango; Schinus sp.,

pepper trees• Araliaceae—Hedera helix, common ivy• Asteraceae—Baccharis sp.• Bromeliaceae—Aechmea, Ananas, Aregelia, Billbergia,

Bromelia, Catopsis, Guzmania, Neoglaziovia, Pitcairnia, Puya, Ronnbergia, Tillandsia, and Vriesia species

• Cactaceae• Cyperaceae• Fabaceae—Acacia, Baikiaea, Cassia, and Leucaena

species• Heliconiaceae• Lauraceae—Persea sp.• Liliaceae• Moraceae—Ficus sp.• Musaceae—Musa sp.• Rosaceae—Rosa sp.• Rubiaceae—Coffea, Dracaena, and Citrus species• Vitaceae—Vitis sp.

4Boisduval Scale, Diaspis boisduvalii Signoret (Insecta: Hemiptera: Diaspididae)

A full listing of recorded hosts for boisduval scale is avail-able at ScaleNet: A Database of Scale Insects of the World.

DamageBoisduval scales are normally found on the leaves and stems of palms. For orchids, this scale tends to prefer the leaf midrib and the portion of the petiole that is covered by the sheath. Boisduval scale is also capable of infesting orchid pseudobulbs and all aerial portions of the plant, including fruit (Miller and Davidson 2005).

ManagementVarious cultural, biological, and chemical control options may be effective for management. Nutritional problems may enhance a host’s susceptibility.

Cultural ControlExclusion is the first measure to be taken to avoid boisduval scale infestation. Carefully examine all plants and propaga-tive materials before purchasing them. However, buyer beware, it is easy to miss scales located underneath leaf sheaths and not all life stages are visible to the unaided eye. New plants should be isolated from collections and nursery stock for at least two weeks to ensure they are pest free. Spacing plants so that their leaves do not touch can help avoid biosduval crawlers moving from infested plants onto clean neighboring plants (Beardsley and Gonzalez 1975). The crawlers can also move from infested to clean plants through strong wind currents in greenhouses and rooms. If possible, isolate infested plants to avoid biosduval scale spread and begin a treatment regimen.

Biological ControlCoccidencyrtus sp. (Hymenoptera: Encyrtidae) have been reported as parasites of boisduval scale (Miller and David-son 2005, Tenbrink and Hara 1992).

Chemical ControlHorticultural oils are often very effective for controlling scale insects, but product labels should be carefully fol-lowed. For example, dormant oils applied to the actively growing stage of a plant may result in a burning effect on the plant material. Because crawlers tend to establish themselves on the upper and lower leaf surfaces, near the base of the plant, and in leaf sheaths, thorough spray coverage is important.

For small amounts of plants, using 70% isopropyl alcohol and a cloth or cotton swab to wipe away the scales can provide effective control. However, some soft-leaved orchids may be damaged by isopropyl.

The American Orchid Society has a helpful on-line video demonstrating how to treat scales with alcohol.

If a chemical application is used, remember that timing the application to target the immature or crawler life stage may be critical for appropriate control. As boisduval scale is an armored scale, the waxy covering may still be present even after it has been effectively killed.

Selected ReferencesBeardsley Jr JW, Gonzalez RH. 1975. The biology and ecology of armored scales. Annual Review of Entomology 20: 47–73.

Figure 7. Chlorosis and pitting caused by boisduval scale, Diaspis boisduvalii Signoret, feeding on Cattleya leaf.Credits: Heidi M. Bowman, UF/IFAS

Figure 8. Coccidencytrus sp., a parasitoid of the boisduval scale, Diaspis boisduvalii Signoret.Credits: Avas Hamon, Florida Department of Agriculture and Consumer Services, Division of Plant Industry

5Boisduval Scale, Diaspis boisduvalii Signoret (Insecta: Hemiptera: Diaspididae)

Buss EA, Dale A. (2016). Scale insects and mealybugs on ornamental plants. MG005. Gainesville: University of Florida Institute of Food and Agricultural Sciences. http://edis.ifas.ufl.edu/MG005 (13 September 2016)

Cating RA, Hoy MA, Palmateer AJ. 2010. Silwet L-77 improves the efficacy of horticultural oils for control of Boisduval scale Diaspis boisduvalii (Hemiptera: Diaspidi-dae) and the flat mite Tenuipalpus pacificus (Arachnida: Acari: Tenuipalpidae) on orchids. Florida Entomologist 93: 100–106. http://journals.fcla.edu/flaent/article/view/76056 (13 September 2016)

Dekle GW. 1965. Arthropods of Florida and Neighboring Land Areas: Florida Armored Scale Insects. Vol.3. Florida Department of Agriculture & Consumer Services, Division of Plant Industry. Gainesville, FL.

Howard FW, Moore D, Giblin-Davis RM, Abad R. 2001. Insects on Palms. CABI Publishing, Wallingford, UK. 400 pp.

Johnson PJ. (November 2001). Scale. American Orchid Society. http://www.aos.org/orchids/orchid-pests-diseases/scale.aspx (13 September 2016)

Miller DR, Gimpel ME. (2009). Diaspididae: Diaspidinae and Leucaspidinae. ScaleNet. http://scalenet.info/ (13 September 2016)

Miller DR, Davidson JA. 2005. Armored Scale Insect Pests of Trees and Shrubs (Hemiptera: Diaspididae). Cornell University Press. Ithaca, NY. 456 pp.

Tenbrink VL, Hara AH. (1992). Diaspis boisduvalli (Signo-ret). Crop Knowledge Master. http://www.extento.hawaii.edu/kbase/crop/Type/d_boisdu.htm (13 September 2016)